In an automatic ice making machine which is so arranged that on the top of a freezing chamber having a plurality of open bottom freezing cells, there is provided an evaporator in a serpentine arrangement which is connected to a refrigeration system, water being sprayed into the freezing cells through a water plate so as to form ice therein, and that the completion of forming of the ice is sensed by a heat-sensitive element so as to supply hot gases to the evaporator and at the same time to incline the water plate downwardly, whereby the ice making machine goes into a defrosting operation, and an amount of water required for one freezing cycle is supplied to the water tank through a water inlet valve under the timing control of a timer. A conventional automatic ice making machine is so arranged that during a defrosting operation, the water plate and the water tank provided thereunder in combination therewith are inclined downwardly to drain all of the water remaining in the tank and defrosting water which has been supplied to the water plate through release from the water inlet valve during a defrosting cycle. Thus, it can be pointed out that to drain all of the water to be frozen which remains in the tank during a defrosting cycle, the defrosting water supplied during the cycle and a small amount of thin ice which has come off the water plate through melting is not only uneconomical due to the increase of water consumption but also responsible for such problems that the freezing time and the amount of electric power consumption are increased due to the fact that all the water to be frozen at ordinary temperature which has been newly supplied to the tank is used in the following freezing cycle.
Therefore, for solving the above-described problems, the present applicant proposed an ice making machine in which a predetermined amount of a mixture of residual water to be frozen which has been used during the previous freezing cycle and has now been sufficiently cooled, and defrosting water which is supplied during a defrosting operation is permitted to remain in the water tank for reuse during the following freezing cycle, whereby the saving of water is effected and at the same time a reduction of freezing time and eletric power consumption is accomplished; and completed the procedure for application for Utility Model Registration of the ice making machine as a Device of "Ice making machine" (Japanese Utility Model Registration Application No. 123246/1983). This ice making machine can achieve great advantageous effects from the viewpoint of saving water to be frozen and a reduction of freezing time; on the other hand, since the machine is adapted to supply water to the water tank through a water inlet valve which opens only for a period of time set by the timer, the machine suffers from the problem of production of incompletely-formed ice cubes due to a shortage of the supply of water to be frozen to the tank during an initial freezing cycle when the power has been initially supplied as in the case of a freezing operation starting after an ice making machine has been newly installed. Accordingly, it can be considered, as a countermeasure against this, that the period of time set by the timer can be lengthened; however, this results in the useless overflow of water to be frozen out of the machine during the second and subsequent freezing cycles because water to be frozen is excessively supplied in view of a necessary amount of water having already been supplied to the water tank, which makes the timer control circuit unsuitable for a water-saving type ice making machine.
The present invention has been newly proposed in order to solve the above-described problems; however, for a better understanding thereof, the outline of an arrangement of a conventional water-saving type ice making machine, and the reason for the occurrence of the aforenoted problems thereto, will be described in more detail precedent to a description of the details of the present invention. FIG. 1 and FIG. 2 show the outline of the arrangement of a water-saving type ice making machine capable of achieving the saving of water to be frozen and the reduction of freezing time, in which reference numeral 10 indicates a freezing chamber formed to provide a plurality of open bottom freezing cells 12 in a checkerboard pattern therein, and on the top surface of the freezing chamber 10 there is closely provided an evaporator 14 in a serpentine arrangement which is connected to a refrigeration system. Under the freezing chamber 10, there is provided a water plate 16 which is pivotally supported at one end thereof by means of a pivot 18 so that the water plate 16 can be freely swung downwardly and upwardly and, which is, at the other end thereof, suspendingly supported by means of a coil spring 17 which is elastically stretched between the leading end of a cam lever 34 and the distal end of the water plate. The cam lever 34 is connected to an actuator motor AM, shown in FIG. 3 which will be described hereinafter, to work in combination therewith, whereby during a defrosting cycle the cam lever is driven by motor AM so as to incline the water plate 16 downwardly and thereby free the bottom of the freezing chamber 10 (See FIG. 2). Also, under the water plate 16, there is adjacently provided a water tank 20 which stores a necessary amount of water to be frozen for one freezing cycle, the water tank 20 also being capable of inclining in combination with the water plate 16. Water to be frozen is supplied to the water tank 20 through means of a water inlet valve WV which is opened and closed under the control of a timer which will be described hereinafter and a feed pipe 22 connected thereto, and this water to be frozen is supplied to a feed tube 26 provided at the bottom of water plate 16 through means of a pump 24 which sprays the water into freezing cell 12 through a plurality of spray nozzles 28 which extend through water plate 16 and also communicate with the feed tube 26. In this connection, it should be noted that the cam lever 34 is equipped with a changeover lever 36 at a predetermined angle which effects the switching of a changeover switch SW shown in FIGS. 1-3, whereby the changeover switch SW is switched to connection of contacts (c-a) in FIG. 3 during the time when the water tank 20 is in a horizontal position, and is switched to connection of contacts (c-b) during the time when the tank is in an inclined-and-stopped position; thereby automatically stopping the water tank 20 in respective positions.
To a side wall of the water tank 20, there is fluidically connected one end of a suitably shaped overflow pipe 30, the other end thereof being open to a drainage pan 38 provided under the tank. When the tank 20 is in a freezing cycle position in which the tank is held in a horizontal position as shown in FIG. 1, level C (for example 6.5 lit.) representing a necessary amount of water to be frozen to be maintained, while at the time of the tank being in a defrosting cycle position in which the tank is in an inclined-and-stopped position, a water amount level D as seen in FIG. 2 (for example 5 lit.) is maintained, in both of the cases the positioning being so arranged that a surplus supply of water is permitted to overflow through overflow pipe 30 into the drainage pan 38 to in turn be drained out of the machine through drainage port 40.
When the freezing operation starts under the condition of the water plate 16 and the water tank 20 being held in a horizontal position as shown in FIG. 1, water to be frozen is sprayed into each freezing cell 12 and cooled by the evaporator 14, forming ice cubes gradually in accordance with the advance of freezing. At this point, in FIG. 3, the changeover switch SW is connected with contacts (c-a), as seen and a freezing sensing thermostatic switch Th.sub.1 is open while a defrosting sensing thermostatic switch Th.sub.2 is closed with contacts (e-g). In addition, normally-open switch TM-a which cooperates with a timer TM is open. As a result of the water to be frozen being consumed in producing ice, the level of the water remaining in the tank 20 at the end of the freezing cycle is lowered to line E (for example 3.2 lit.) as seen in FIG. 1. In this connection, it should be noted that water remaining unfrozen in each freezing cell 12 is collected in the tank 20 through means of a plurality of drainage holes 32 formed within plate 16 adjacent to each spray nozzle 28 so as to be pumped again by means of pump 24 for circulation.
When the forming of ice cubes is completed, the freezing-sensing thermostatic switch Th.sub.1 shown in FIG. 3 operates to close the contacts thereof, and through such contacts and the contacts (c-a) of the changeover switch SW the actuator motor AM is energized, whereby the cam lever 34 is turned around so as to downwardly incline the water plate 16 and the water tank 20 as shown in FIG. 2. In accordance with the turning-around movement of the cam lever 34, the changeover lever 36 provided thereon causes the changeover switch SW to switch to the connection between the contacts (c-b). This energizes a hot valve HV through the contacts (e-g) of the defrosting sensing thermostatic switch Th.sub.2 so as to open the valve whereby hot gases are supplied to the evaporator 14 to heat the freezing cells 12, thereby accelerating the discharge of ice cubes therefrom. The changeover operation of the switch SW de-energizes the water inlet valve controlling timer circuit TM, closing normally-open time limit switch TM-a which cooperates with a relay X incorporated in the timer circuit TM, thereby opening the water inlet valve WV so as to supply defrosting water to the water plate 16 through means of the feed pipe 22. The defrosting water not only melts thin ice formed on the water plate so as to thereby cause the thin ice to come off but is also cooled by heat exchange and then collected within the water tank 20. This supply of defrosting water is continued for a predetermined time even after the defrosting sensing thermostatic switch Th.sub.2 has sensed the discharge of ice cubes and caused the water tank 20 to return to its original position, whereby the remaining water to be frozen in the tank 20 which has become somewhat lower in quality is mixed and diluted with the defrosting water so as to thereby prevent further deterioration of the quality of the water. In this connection, it should be noted that when the tank is in its inclined-and stopped position, the level of the mixture of the water is maintained at the level D (for example 5 lit.) by means of the overflow pipe 30.
In accordance with the advance of the defrosting cycle, the contacts of the freezing sensing thermostatic switch Th.sub.1 are reset to the open (OFF) position, and then all the ice cubes are simultaneously discharged from their respective freezing cells 12 so as to slide down the water plate 16 to be collected in an ice cube bin (not shown). When the contacts (e-g) of the defrosting sensing thermostatic switch Th.sub.2 open, the other contacts (e-f) of switch Th.sub.2 are simultaneously closed so as to reversely drive the motor AM whereby the water plate 16 and the water tank 20 are moved back to their original positions as shown in FIG. 1. During this time, the hot valve HV is closed so as to stop the supply of hot gases, and the flow of refrigerant gases is also restarted. This returning action of plate 16 and tank 20 accompanies the resetting of the connection of the changeover switch SW to the position of contacts (c-a) thereby re-energizing the timer TM whereby the water inlet valve WV is kept open for a predetermined period of time (for example 5 seconds) so as to supply water to the water tank 20 until the water therein rises to level C (for example 6.5 lit.) which is the necessary amount of water required for a freezing operation, and then the normally-open contacts TM-a open so as to close the water inlet valve WV. The timing chart of the freezing cycle and the defrosting cycle described heretofore is shown in FIG. 4.
Next, the relationship between the amount of water supplied to the water tank 20 and the water supplying time will be discussed. Now, let it be assumed that the amount of water supplied through the water inlet valve WV is 3 lit./minute, while the necessary amount of water to be frozen within one freezing cycle is 6.5 lit. (level C in FIG. 1). Here, the experimental measurement using an existing apparatus of the time for keeping the water inlet valve WV open shows 100 seconds and the details thereof are as follows:
(A) Time during which the water tank is in an inclined-and-stopped position (T.sub.1): 60 seconds.
(B) Time during which the water tank rises back to its original position (T.sub.2): 35 seconds.
(C) Preset period of time during which the timer TM operates after being energized before the cooperating contacts TM-a thereof open (T.sub.3): 5 seconds.
When the water tank 20 is in an inclined-and-stopped position, the water to be frozen which has remained within tank 20 after consumption in the preceding freezing cycle is 3.2 lit. (level E in FIG. 1) as described hereinbefore, and to this water there is supplied 3 lit. of defrosting water over a period of time (T.sub.1) of 60 seconds while the tank is in an inclined-and-stopped position, the total of the water therefore amounting to 6.2 lit. Accordingly, the amount of water in the tank 20 in an inclined-and-stopped position comes to exceed the water level D which corresponds to 5 lit., this amount of the water mixture comprising the total of the water to be frozen remaining in tank 20, and the defrosting water added thereto, as determined or maintained by the overflow tube 30. Besides, 2 lit. of new water is supplied over a period of time (T.sub.2) of 35 seconds which is the time required for swinging the water tank back to its original position and a subsequent period of time (T.sub.3) of 5 seconds during which the supply of water through the water inlet valve WV is continued by the timer TM; accordingly, in the tank 20 which has been swung back to its horizontal position, the water sufficient for 6.5 lit., the amount which is necessary for a freezing operation is achieved. In addition, any surplus amount of the water is drained out of the machine through the overflow pipe 30.
Although there is no problem so long as the usual freezing cycles are repeated, since the water quality is improved by mixing water to be frozen remaining in the tank with newly supplied water and the saving of water to be frozen in tank 20 and a reduction of freezing time are also effected; when an initial freezing cycle starts as in the case of a newly-installed ice making machine starting a freezing operation, the following inherent problems arise. For example, in an initial freezing cycle, the water to be frozen and remaining in the water tank 20 is zero, and moreover, the freezing cells are also at ordinary temperature and not as yet cooled, with the defrosting sensing thermostatic switch Th.sub.2 being connected between the contacts (e-f) in FIG. 3. Upon energizing the ice making machine, the water tank 20 swings and changes the connection of the changeover switch SW to that of contacts (c-b), whereby the water tank 20 starts swinging upwardly. In this state, the water inlet valve WV opens for 40 seconds, and the details of the time are as follows:
(A) Time during which the water tank is in an inclined-and-stopped position: 0 seconds.
(B) Time during which the water tank starts swinging upwardly and completes entering into a freezing operation stand-by position: 35 seconds.
(C) Time until the water inlet valve WV is opened by the timer TM: 5 seconds.
The amount of water to be frozen supplied to the tank 20 during the 40 seconds is 2 lit., which brings about a great shortage of 4.5 lit. relative to 6.5 lit., which is the necessary amount of water to be frozen within one freezing cycle. When the initial freezing operation is carried out under such a condition that the water to be frozen is insufficient, the ice cubes formed are incompletely shaped and the weight of each cube is insufficient. As a countermeasure against the shortage of the supply water at the start of an initial freezing cycle, it is only necessary that the timer TM be predetermined for a longer set period of time, thereby prolonging the time for keeping the water inlet valve WV open so as to compensate for the insufficient amount of the supply water; however, the time for keeping the valve open which is considered to be necessary for the supply of the insufficient amount of water, 4.5 lit., amounts to as long as 50 seconds. Accordingly, at the start of an initial freezing cycle, the necessary amount of water can be provided during the preset time (T.sub.3) of 95 seconds; however, during the second freezing cycle and subsequent freezing cycles thereafter, an excess of 4.5 lit. of water is drained out of the machine since the preset period of time T.sub.3 of the timer TM, for which 5 seconds is sufficient, exceeds the necessary period of time by 90 seconds (95 seconds minus 5 seconds), which makes the timer control circuit unsuitable for use in the water-saving type ice making machine.